Girbl, TamaraLenn, TchernPerez, LorenaRolas, LoïcBarkaway, AnnaThiriot, Audedel Fresno, CarlosLynam, EleanorHub, ElinThelen, MarcusGraham, GerardAlon, RonenSancho, Davidvon Andrian, Ulrich HVoisin, Mathieu-BenoitRot, AntalNourshargh, Sussan2019-02-072019-02-072018-12-18Immunity. 2018; 49(6):1062-761074-7613http://hdl.handle.net/20.500.12105/7143Neutrophils require directional cues to navigate through the complex structure of venular walls and into inflamed tissues. Here we applied confocal intravital microscopy to analyze neutrophil emigration in cytokine-stimulated mouse cremaster muscles. We identified differential and non-redundant roles for the chemokines CXCL1 and CXCL2, governed by their distinct cellular sources. CXCL1 was produced mainly by TNF-stimulated endothelial cells (ECs) and pericytes and supported luminal and sub-EC neutrophil crawling. Conversely, neutrophils were the main producers of CXCL2, and this chemokine was critical for correct breaching of endothelial junctions. This pro-migratory activity of CXCL2 depended on the atypical chemokine receptor 1 (ACKR1), which is enriched within endothelial junctions. Transmigrating neutrophils promoted a self-guided migration response through EC junctions, creating a junctional chemokine "depot" in the form of ACKR1-presented CXCL2 that enabled efficient unidirectional luminal-to-abluminal migration. Thus, CXCL1 and CXCL2 act in a sequential manner to guide neutrophils through venular walls as governed by their distinct cellular sources.engVoRhttp://creativecommons.org/licenses/by/4.0/ACKR1CXCR2ChemokinesEndotheliumExtravasationInflammationNeutrophilsPericytesAtribución 4.0 Internacional304463884961062-1076.e610.1016/j.immuni.2018.09.0181097-4180Immunityopen access